An known image forming apparatus includes process cartridges (image forming unit) each of which includes a photosensitive drum, a belt unit which is disposed below and opposes the photosensitive drums and includes a belt for conveying a sheet between the belt and the photosensitive drums, and a drawer which holds the process cartridges integrally and can be drawn out from a main body. In this technique, when a maintenance of the belt unit or the periphery thereof (e.g., exchange, cleaning, and fixing paper jam) is performed, the drawer is detached from the main body, and thereafter the belt unit is detached from the main body through a space in the main body made by detaching the drawer.
Each of the process cartridges is connected to a drive source of the main body, e.g., via a coupling, so as to transmit driving force from the drive source to components of each of the process cartridge (e.g., a photosensitive drum). Therefore, when the maintenance is performed, the user or worker conducts a work to cut the connection between the driving source of the main body and the process cartridges and thereafter to pull out the drawer.